Mechanical and chemical-mechanical planarization processes (collectively “CMP”) remove material from the surface of micro-device workpieces in the production of microelectronic devices and other products. FIG. 1 schematically illustrates a rotary CMP machine 10 with a platen 20, a carrier head 30, and a planarizing pad 40. The CMP machine 10 may also have an under-pad 25 between an upper surface 22 of the platen 20 and a lower surface of the planarizing pad 40. A drive assembly 26 rotates the platen 20 (indicated by arrow F) and/or reciprocates the platen 20 back and forth (indicated by arrow G). Since the planarizing pad 40 is attached to the under-pad 25, the planarizing pad 40 moves with the platen 20 during planarization.
The carrier head 30 has a lower surface 32 to which a micro-device workpiece 12 may be attached, or the workpiece 12 may be attached to a resilient pad 34 under the lower surface 32. The carrier head 30 may be a weighted, free-floating wafer carrier, or an actuator assembly 36 may be attached to the carrier head 30 to impart rotational motion to the micro-device workpiece 12 (indicated by arrow J) and/or reciprocate the workpiece 12 back and forth (indicated by arrow 1).
The planarizing pad 40 and a planarizing solution 44 define a planarizing medium that mechanically and/or chemically-mechanically removes material from the surface of the micro-device workpiece 12. The planarizing solution 44 may be a conventional CMP slurry with abrasive particles and chemicals that etch and/or oxidize the surface of the micro-device workpiece 12, or the planarizing solution 44 may be a “clean” nonabrasive planarizing solution without abrasive particles. In most CMP applications, abrasive slurries with abrasive particles are used on nonabrasive polishing pads, and clean nonabrasive solutions without abrasive particles are used on fixed-abrasive polishing pads.
To planarize the micro-device workpiece 12 with the CMP machine 10, the carrier head 30 presses the workpiece 12 face-down against the planarizing pad 40. More specifically, the carrier head 30 generally presses the micro-device workpiece 12 against the planarizing solution 44 on a planarizing surface 42 of the planarizing pad 40, and the platen 20 and/or the carrier head 30 moves to rub the workpiece 12 against the planarizing surface 42. As the micro-device workpiece 12 rubs against the planarizing surface 42, the planarizing medium removes material from the face of the workpiece 12.
The CMP process must consistently and accurately produce a uniformly planar surface on the micro-device workpiece 12 to enable precise fabrication of circuits and photo-patterns. One problem with conventional CMP methods is that the planarizing surface 42 of the planarizing pad 40 can wear unevenly or become glazed with accumulations of planarizing solution 44 and/or material removed from the micro-device workpiece 12 and/or planarizing pad 40. To restore the planarizing characteristics of the planarizing pad 40, the pad 40 is typically conditioned by removing the accumulations of waste matter with an abrasive conditioning disk 50. The conventional abrasive conditioning disk 50 is generally embedded with diamond particles and mounted to a separate actuator 55 that moves the conditioning disk 50 rotationally, laterally, and/or axially, as indicated by arrows A, B, and C, respectively. The typical conditioning disk 50 removes a thin layer of the planarizing pad material in addition to the waste matter to form a new, clean planarizing surface 42 on the planarizing pad 40.
During the conditioning process, the conditioning disk 50 imparts texture to the planarizing pad 40. One problem with conventional conditioning methods is that even if the conditioning disk 50 uniformly removes the planarizing pad material, different textures are formed across the planarizing pad 40. Differences in texture across the planarizing pad 40 can cause the pad 40 to remove material at different rates across the micro-device workpiece 12 during the CMP process. Differences in texture can also produce defects on the micro-device workpiece 12. Consequently, the CMP process may not produce a uniformly planar surface on the micro-device workpiece 12.